Perhaps the fanfiction keeps rehashing the same tired storylines about Konoha. Naruto might be tired of seeing the same things over and over again, like always focusing on the village's dark secrets in a clichéd way instead of exploring new aspects of Konoha and its people.
Perhaps Naruto is fed up with Konoha's fanfiction because he wants a new adventure outside of the village. He has spent most of his life in Konoha and might be craving for a change. He could be bored with the same old politics and power struggles within the village. Also, he may have realized that the ideals of Konoha are not as perfect as they seem, and this disillusionment makes him tired of it.
On the positive side, it could inspire new and more creative fanfiction. Fans might try to write stories that Naruto would approve of, exploring different angles of Konoha and his relationship with the village in a more positive and nuanced way to avoid making him fed up.
Well, it might be that the fanfiction focuses too much on Sakura in a way that Naruto feels is unfair to the other characters. Naruto is part of a big world with many important people, and if the fanfic just hones in on Sakura all the time, he could get fed up. Also, if the fanfiction has Sakura constantly putting Naruto down or not appreciating his efforts like in the real story, that could be a reason.
One reason could be that in some fanfictions, the characters of Team 7 are portrayed out of character. Naruto might be fed up if they make Sasuke too brooding in a way that doesn't seem true to the original. Also, if the fanfiction focuses too much on shipping within Team 7, like Sasuke and Sakura, and ignores Naruto's growth and importance, it could annoy him. Another possibility is if the fanfiction makes the team seem too dysfunctional in a way that doesn't match Naruto's view of his comrades.
It could lead to a shift in the type of fanfictions being produced. If Naruto getting fed up with Sakura fanfiction becomes a popular concept, more fanfic writers might avoid writing in that vein or might try to rewrite the relationship in a more acceptable way, which in turn changes the overall landscape of Naruto fanfictions in the fandom.
If Naruto gets fed up with Team 7 fanfiction, some fans who love Naruto's perspective might stop reading those fanfictions. This could lead to a decrease in the popularity of certain types of Team 7 fanfictions. Writers might then have to change their approach to keep their readers.
His relationship with some friends might become strained. For instance, if Naruto decides to leave Konoha, some friends who are more loyal to the village might oppose his decision. However, his true friends will try to understand his reasons. Sakura, for example, might initially be shocked but then come to terms with it as she has seen Naruto's struggles.
One possible reason could be jealousy. Naruto is very powerful and some in Konoha might be envious. For example, some minor clans might feel that Naruto, as an outsider in a sense, gets too much attention and resources. Another reason could be fear. His Nine - Tails power is so immense that some might fear he could lose control and endanger the village, so they betray him to try and eliminate the 'threat' before it's too late.
One reason could be the lack of recognition he gets in the village despite his great contributions. In the fanfiction, Naruto might feel that his efforts to protect the village are taken for granted.